Wireless base station, wireless frames synchronization detection method used therein, and recording medium on which program therefor is recorded

ABSTRACT

In a baseband processing unit in a node-B, a path search circuit includes a path capture unit, path track transfer unit, and channel estimation unit, all of which are primarily provided for the path capture, channel estimation, and RAKE combination. In the baseband processing unit, a synchronization determination circuit includes a decoding unit provided for decoding RAKE-combined data and calculating an average SIR per wireless frame and a correction calculation unit primarily provided for reliably and stably detecting wireless frame synchronization. The processing time required to detect synchronization establishment during wireless frame synchronization determination is shortened.

BACKGROUND OF THE INVENTION

The present invention relates to a wireless base station, a wirelessframe synchronization detection method used therein, and a recordingmedium on which a program therefor is recorded and, more particularly,to a wireless frame synchronization detection method of detectingwireless frame synchronization in a wireless base station (node-B) whichperforms communication by using the CDMA (Code Division Multiple Access)method.

The conventional general wireless frame synchronization method in node-Bdescribed in “W-CDMA (Wideband Code Division Multiple Access) MobileCommunication Method” (supervised by Keiji Tatekawa, and issued on Jun.25, 2001 by Maruzen Kabushiki Kaisha)” will be described below.

The CDMA method describes the definitions of a transmission channel andphysical channel, and the explanation of the definitions. The physicalchannel normally has a hierarchical arrangement including wirelessframes and time slots, and the forms of the wireless frames and timeslots change in accordance with the symbol rate of the physical channel.

The wireless frame is made up of 15 time slots, and is a minimum unit ofsignal processing. The time slot is a minimum constituting unit of alayer 1-bit sequence, and is a minimum processing unit of transmit powercontrol and a channel estimation process. The number of bits in one timeslot depends upon the physical channel.

Of the physical channels described above, in an uplink DPCH (DedicatedPhysical Channel), two types, i.e., a DPDCH (Dedicated Physical DataChannel) used for data transmission and a DPCCH (Dedicated PhysicalControl Channel) used to transmit physical control information aremultiplexed by I/Q [In-phase/Quadrature] for each wireless frame.

The DPCCH for handling control information is made up of pilot bits(Pilot) having a known pattern used for estimation in synchronizationdetection, a transmit power control command (TPC: Transmit PowerControl), feedback information (FBI: Feedback Information), and a TFCI(Transport Format Combination Indicator).

FIG. 9 shows the wireless frame arrangement of the uplink DPCCHdescribed above. Referring to FIG. 9, each wireless frame (10 ms) isdivided into 15 slots, and one slot has 2,560 chips. The number of bitsper slot of the uplink DPDCH/DPCCH is determined by a parameter k, andthe parameter k corresponds to SF (Spreading Factor)=256/2 k of thephysical channel. The SF of the DPDCH is set within the range of 256 to4, and 256 (a fixed value) is set as the SF of the DPCCH. A slot formatto be used in the DPCCH is determined by the use/nonuse of the TFCI, theuse (the number of bits used)/nonuse of the FGI, and the application(the number of transmission slots)/non-application of a compressionmode.

The CDMA method performs channel estimation by using the pilot bits, anddetects frame synchronization by using an SW (Sync Word) contained inthe pilot bits. As shown in FIG. 10, the conventionally general wirelessframe synchronization detection method detects wireless framesynchronization establishment and synchronization pull out by using thecorrelation characteristics of the SW.

That is, in this wireless frame synchronization detection method, thepilot bits of the uplink DPCCH received in node-B are compared with areference pilot bit pattern used for channel estimation, and, if thenumber of mismatch bits is equal to or smaller than a preset number ofpilot error allowable bits, it is determined that pilot bit reception isOK.

Also, in the wireless frame synchronization detection method, if thispilot bit OK state continues for a predetermined frame period (acritical value used in this determination is called the number of framesynchronization backward protection steps), it is determined thatwireless frame synchronization establishment is detected, and, if thepilot bit reception NG state continues for the predetermined frameperiod (a critical value used in this determination is called the numberof frame synchronization forward protection steps), it is determinedthat wireless frame synchronization pull out is detected.

Referring to FIG. 10, in the above wireless frame synchronizationdetection method, after the start of synchronization establishment,pilot bit reception OK detection is started from wireless framesynchronization state=initial state (A), and, if a wireless frame periodin which pilot bit reception is OK continues and becomes equal to orlarger than the critical value: the number of frame synchronizationbackward protection steps, the process advances to wireless framesynchronization state=synchronization establishment (B) (a in FIG. 10).

Also, in the wireless frame synchronization detection method, pilot bitreception NG detection is started from wireless frame synchronizationstate=synchronization establishment (B), and, if a wireless frame periodin which pilot bit reception is NG continues and becomes equal to orlarger than the critical value: the number of frame synchronizationforward protection steps, the process advances to wireless framesynchronization state=synchronization pull out (C) (b in FIG. 10).

In addition, in the wireless frame synchronization detection method,pilot bit reception OK detection is started from wireless framesynchronization state=synchronization pull out (C), and, if a wirelessframe period in which pilot bit reception is OK continues and becomesequal to or larger than the critical value: the number of framesynchronization backward protection steps, the process advances towireless frame synchronization state=synchronization establishment (B)(c in FIG. 10).

Furthermore, in the wireless frame synchronization detection method, acall is released from wireless frame synchronizationstate=synchronization establishment (B), or from wireless framesynchronization state=synchronization pull out (C), and the processadvances to wireless frame synchronization state=initial state (A) (d inFIG. 10).

In the conventional general wireless frame synchronization detectionmethod described above, however, the pilot error allowable bits and thenumber of frame synchronization protection steps used in the method arearbitrarily set for each node-B, so the standards for wireless framesynchronization establishment detection and synchronization pull outdetection change in accordance with an arbitrary combination of a UE(User Equipment: mobile station) and node-B.

Accordingly, unified standards for wireless frame synchronizationestablishment detection, synchronization pull out detection, andsynchronization maintenance detection are required even in an arbitraryUE and node-B, and a method of determining wireless framesynchronization by a more accurate method is being studied.

Also, in the conventional wireless frame synchronization determinationmethod, wireless frame synchronization establishment may be detected byerror in a wireless frame even if no upward signal is received. This ispresumably caused by the following mechanism.

In a path capture process, a plurality of paths may be notified to achannel estimation means, even if there is no signal, depending on theset value of a path detection threshold. If channel estimation isperformed for each path and phase correction is performed for the pathby using a carrier wave phase having the highest correlation to thepilot bit pattern, a value closer to the pilot bit pattern than thatwhen the output value of each path is random may be obtained.

Furthermore, if pilot bits output by RAKE combination of the value areequal to or smaller than the pilot error allowable bits, asynchronization establishment error occurs in a wireless frame.

This phenomenon occurs extremely generally not only in the CDMA systembut also in any wireless system in which phase estimation is performedusing the pilot bits, and wireless frame synchronization is determinedusing the pilot bit pattern after RAKE combination.

The foregoing is also obvious from the results of the simple simulationdescribed below, and it is possible to confirm that a synchronizationestablishment error surely occurs by the above mechanism. The conditionsof individual items in the channel estimation means used during thesimulation are as shown in FIG. 11.

White noise is used as an input signal, and the weighted mean of thechannel estimation values of two forward time slots and two backwardtime slots (a total of five time slots) is calculated, therebyestimating an FV (Fading Vector). This FV is used to perform phasecorrection and RAKE combination for the input signal, the degree ofmatching between an FSW (Frame Synchronous Word) contained in the signaland a transmission pattern is checked, and it is found that the FSW isfour symbols out of six symbols of the pilot bit pattern per slot, and atotal of 60 symbols are contained in one wireless frame.

FIG. 12 shows the simulation results plotted as a histogram. When nophase correction is performed, a wide distribution centering around 30symbols is obtained as expected. When phase correction is performed, thecenter is around 40 symbols even when the number of captured paths is 1(unit: path), and the degree of matching increases after that as thenumber of captured paths increases. When the number of captured paths is10 (unit: path), the degree of matching reaches 56 or 57 symbols.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wireless basestation capable of reducing the processing time before synchronizationestablishment is detected in wireless frame synchronizationdetermination, a wireless frame synchronization detection method usedtherein, and a recording medium on which a program therefor is recorded.

A first wireless base station according to the present invention is awireless base station which communicates by a CDMA (Code DivisionMultiple Access) method, comprising path capture means for setting atemporary captured path near a preset propagation delay when a signal isreceived from a state in which no upward signal is input, and performinga normal path capture process for the input signal.

A second wireless base station according to the present inventionfurther comprises, in addition to the above arrangement, path tracktransfer means for transferring path information captured by the pathcapture means to a new resource capable of processing, if processingcannot be performed due to hard handover control, wherein the pathcapture means performs the normal path capture process by using the pathinformation from an original resource.

A third wireless base station according to the present invention furthercomprises, in addition to the above arrangement, channel estimationmeans for performing channel estimation, RAKE combination, andsignal-to-interference ratio measurement per slot for a path captured bythe path capture means, decoding means for decoding a RAKE-combinedpilot data sequence obtained by the channel estimation means, andcalculating an average per wireless frame of the signal-to-interferenceratios measured for individual slots, and correction calculation meansfor determining whether pilot bit reception is OK or NG on the basis ofpilot bit information per wireless frame decoded by the decoding means,and determining whether signal-to-interference ratio determination is OKor NG with respect to signal-to-interference ratio average informationmeasured by the decoding means, the correction calculation meanscomprising a pilot bit determination unit which determines whether pilotbit reception is OK or NG, an SIR determination unit which determineswhether signal-to-interference ratio determination is OK or NG, and asynchronization establishment determination unit which determineswireless frame synchronization by using results of the determination ofpilot bit reception OK/NG and the determination ofsignal-to-interference ratio determination OK/NG.

A fourth wireless base station according to the present invention hasthe above arrangement in which the pilot bit determination unitdetermines whether pilot bit reception is OK or NG on the basis of aparameter based on the number of pilot bits in an uplink DPCCH(Dedicated Physical Control Channel) per wireless frame when all slotsof one wireless frame are received when an up slot format to be usedchanges, and a critical value for performing the determination of pilotbit reception OK/NG in wireless frame synchronization determination.

A first wireless frame synchronization detection method according to thepresent invention is a wireless frame synchronization detection methodof determining wireless frame synchronization in a wireless base stationwhich communicates by a CDMA (Code Division Multiple Access) method,comprising the steps of setting a propagation delay, setting a temporarycaptured path near the propagation delay when a signal is received froma state in which no upward signal is input, and performing a normal pathcapture process for the input signal.

A second wireless frame synchronization detection method according tothe present invention further comprising, in addition to the aboveprocesses, the steps of transferring path information captured by thenormal path capture process to a new resource capable of processing, ifprocessing cannot be performed due to hard handover control, andperforming the normal path capture process by using the path informationfrom an original resource.

A third wireless frame synchronization detection method according to thepresent invention further comprises, in addition to the above processes,the steps of performing channel estimation, RAKE combination, andsignal-to-interference ratio measurement per slot for a path captured bythe normal path capture process, decoding a RAKE-combined pilot datasequence, calculating an average per wireless frame of thesignal-to-interference ratios measured for individual slots, determiningwhether pilot bit reception is OK or NG on the basis of decoded pilotbit information per wireless frame, determining whethersignal-to-interference ratio determination is OK or NG with respect tosignal-to-interference ratio average information, and determiningwireless frame synchronization by using results of the determination ofpilot bit reception OK/NG and the determination ofsignal-to-interference ratio determination OK/NG.

In a fourth wireless frame synchronization detection method according tothe present invention, the step of determining whether pilot bitreception is OK or NG comprises the step of determining whether pilotbit reception is OK or NG on the basis of a parameter based on thenumber of pilot bits in an uplink DPCCH (Dedicated Physical ControlChannel) per wireless frame when all slots of one wireless frame arereceived when an up slot format to be used changes, and a critical valuefor performing the determination of pilot bit reception OK/NG inwireless frame synchronization determination.

A first computer-readable recording medium recording a program of awireless frame synchronization detection method according to the presentinvention is a computer-readable recording medium recording a program ofa wireless frame synchronization detection method of determiningwireless frame synchronization in a wireless base station whichcommunicates by a CDMA (Code Division Multiple Access) method, whereinthe program comprises a program which allows a computer to function aspath capture means for setting a temporary captured path near a presetpropagation delay when a signal is received from a state in which noupward signal is input, and performing a normal path capture process forthe input signal.

A second computer-readable recording medium recording the program of thewireless frame synchronization detection method according to the presentinvention further comprises, in addition to the above processes, aprogram which allows a computer to function as path track transfer meansfor transferring path information captured by the normal path captureprocess to a new resource capable of processing, if processing cannot beperformed due to hard handover control, and as path capture means forperforming the normal path capture process by using the path informationfrom an original resource.

A third computer-readable recording medium recording the program of thewireless frame synchronization detection method according to the presentinvention further comprises, in addition to the above processes, aprogram which allows a computer to function as channel estimation meansfor performing channel estimation, RAKE combination, andsignal-to-interference ratio measurement per slot for a path captured bythe normal path capture process, decoding means for decoding aRAKE-combined pilot data sequence, and calculating an average perwireless frame of the signal-to-interference ratios measured forindividual slots, and correction calculation means for performing thewireless frame synchronization determination by determining whetherpilot bit reception is OK or NG on the basis of decoded pilot bitinformation per wireless frame, and determining whethersignal-to-interference ratio determination is OK or NG with respect tosignal-to-interference ratio average information.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the arrangement of a node-B accordingto an embodiment of the present invention;

FIGS. 2A to 2E are block diagrams showing the arrangement of the node-Baccording to the embodiment of the present invention;

FIG. 3 is a flowchart showing a wireless frame synchronizationdetermination process performed by correction calculation means shown inFIG. 1;

FIG. 4 is a flowchart showing the wireless frame synchronizationdetermination process performed by the correction calculation meansshown in FIG. 1;

FIG. 5 is a flowchart showing the wireless frame synchronizationdetermination process performed by the correction calculation meansshown in FIG. 1;

FIG. 6 is a view showing the wireless frame structure of an uplink DPCCHin the CDMA method;

FIG. 7 is a view showing pilot bit patterns when the Npilot data sizesof an uplink DPCCH are 3, 4, 5, and 6 bits;

FIG. 8 is a view showing pilot bit patterns when the Npilot data sizesof the uplink DPCCH are 7 and 8 bits;

FIG. 9 is a view showing the wireless frame structure of the uplinkDPCCH in the CDMA method;

FIG. 10 is a view showing the transition of a general wireless framesynchronization detection method in the CDMA method;

FIG. 11 is a view showing the conditions of individual items in channelestimation means used in simulation; and

FIG. 12 is a graph in which the simulation results are plotted as ahistogram.

DESCRIPTION OF THE EMBODIMENT

An embodiment of the present invention will be described below withreference to the accompanying drawings. FIG. 1 is a block diagramshowing the arrangement of a node-B (wireless base station) according tothe embodiment of the present invention. This node-B according to theembodiment of the present invention includes baseband processing units 1and 2, and a recording medium 3 connected to the baseband processingunits 1 and 2. The baseband processing units 1 and 2 can operateindependently of each other.

Although the node-B according to this embodiment has the two basebandprocessing units 1 and 2, it is easy to use an arbitrary number ofbaseband processing units, and give individual circuits and means inthese baseband processing units in the same arrangements as the basebandprocessing units 1 and 2 shown in FIG. 1.

The baseband processing units 1 and 2 include path search circuits 11and 21 having path capture means 12 and 22, path track transfer means 13and 23 connected to the path capture means 12 and 22, and channelestimation means 14 and 24 connected to the path capture means 12 and22, respectively. The baseband processing units 1 and 2 also includesynchronization determination circuits 15 and 25 having decoding means16 and 26 connected to the channel estimation means 14 and 24, andcorrection calculation means 17 and 27 connected to the decoding means16 and 26, respectively.

As shown in FIG. 2A, the path capture means 12 includes a captured pathallocation unit 12 a which arbitrarily allocates a temporary capturedpath near a propagation delay which is set from a host apparatus (notshown) to the node-B (not shown) when a wireless link is set in a statein which no up carrier is present, and a normal path capture unit 12 bwhich performs a normal path capture process for an input signal from asignal line 100. The path capture means 22 has the same arrangement.

The path capture means 12 and 22 also have interfaces with the channelestimation means 14 and 24, and transfer the information of capturedpaths to the channel estimation means 14 and 24 via signal lines 111 and121, respectively. Furthermore, the path capture means 12 and 22 haveinterfaces with the path track transfer means 13 and 23, performtransfer of the information of captured paths to the path track transfermeans 13 and 23 and read of the information of paths transferred fromthe path track transfer means 13 and 23 via signal lines 112 and 122,respectively.

That is, in a wireless frame synchronization method using determinationby a pilot bit pattern and determination by an SIR(Signal-to-Interference Ratio), even when receiving a signal from astate in which no upward signal is input to the path search circuit 11of the baseband processing unit 1 in the node-B (wireless base station),the path capture means 12 reduces the pull-in required time beforewireless frame synchronization establishment, and holds this time withina predetermined time.

The path capture means 12 and 22 have the function of allocating atemporary captured path near a propagation delay set from a hostapparatus to the node-B when a wireless link is set from a state inwhich no upward signal is present, thereby reducing the time before anormal path is captured. In this case, the number of paths to beallocated for temporary capture is equal to or smaller than the maximumnumber of paths which can be captured. However, this number need not beany predetermined value, and can take a value of 1 (unit: path) or more.

As shown in FIG. 2B, the path track transfer means 13 has a storage unit13 b for storing the information of a path transferred from the pathcapture means 12 via the signal line 112. The path track transfer means13 also has a communication unit 13 a which has an interface with thepath track transfer means 23, and, if the baseband processing unit 1becomes unable to continue processing, transfers, via a signal line 200,the stored path information to the path track transfer means 23 capableof processing. The path track transfer means 13 has the samearrangement.

On the basis of the path information transferred from the path tracktransfer means 13, the path track transfer means 23 transfers the pathinformation to the path capture means 22 via the signal line 122, inorder to allow the baseband processing unit 2 to continuously capturepaths.

That is, when the path search circuit of the baseband unit in the node-Bperforms hard handover control, the path track transfer means 13 or 23stores the state before handover, and transfers the path information tothe destination of handover to make continuous path track possible.

When different-frequency hard handover or non-break hard handovercontrol is to be performed for a call currently being communicated inthis path track transfer means, if this resource cannot be processed dueto the mechanism or processability of each node-B, the communication iscontinued by handing the processing over to a new resource. In thiscase, the path information captured by the original resource is stored,and the stored path information is transferred to the new resource tomake continuous path track possible. The number of paths captured andstored in the original resource and the number of paths to betransferred to the new resource is 0 (unit: path) or more, and equal toor smaller than the maximum number of paths, on the basis of the stateof path capture in the original resource.

As shown in FIG. 2C, the channel estimation means 14 and 24 include anestimation unit 14 a and RAKE combination unit 14 b for performingchannel estimation and RAKE combination, respectively, for pathscaptured by the path capture means 12 and 22, and an SIR measurementunit 14 c for measuring the SIR for each slot. The channel estimationmeans 14 and 24 also include a communication unit 14 d which has aninterface with the decoding means 16 and 26 in the synchronizationdetermination circuits 15 and 25, and transfers the RAKE-combined pilotdata sequence and the SIR measurement results of individual slots viasignal lines 113 and 123.

That is, the channel estimation means 14 and 24 perform channelestimation, RAKE combination, and SIR measurement for each slot on thebasis of the path information captured in the path search circuit of thebaseband processing unit in the node-B by the path capture means andpath track transfer means.

As shown in FIG. 2D, the decoding means 16 and 26 include a decodingunit 16 a for decoding the RAKE-combined pilot data sequence obtained bythe channel estimation means 14 and 24, and an averaging unit 16 b whichcalculates the average per wireless frame of the SIRs measured forindividual slots. The decoding means 16 and 26 also include acommunication unit 16 c which has an interface with the correctioncalculation means 17 and 27, and transfers the decoded pilot bitinformation and the average SIR information per wireless frame viasignal lines 114 and 124.

That is, the decoding means 16 decodes, in the synchronizationdetermination circuit 15 of the baseband processing unit in the node-B,the RAKE-combined pilot data sequence per wireless frame obtained by thechannel estimation means in the path search circuit, and measures theaverage SIR per wireless frame.

As shown in FIG. 2E, the correction calculation means 17 and 27 includean operation unit 17 a which, on the basis of the one-wireless-framepilot bit information decoded by the decoding means 16 and 26,calculates critical values “the number of post-correction backwardprotection pilot error allowable bits” and “the number ofpost-correction forward protection pilot error allowable bits” to beused when wireless frame synchronization determination is actuallyperformed, from a parameter “the number of standard slot format pilotbits” and critical values “the number of backward protection pilot errorallowable bits” and “the number of forward protection pilot errorallowable bits” by using a correction calculation method represented byequation (1) to be presented later, and a pilot bit determination unit17 b which determines pilot bit reception OK/NG with respect to “thenumber of post-correction backward protection pilot error allowablebits” and “the number of post-correction forward protection pilot errorallowable bits”.

The correction calculation means 17 and 27 also include a storage unit17 e which stores the parameter “the number of standard slot formatpilot bits” and the critical values “the number of backward protectionpilot error allowable bits” and “the number of forward protection piloterror allowable bits”.

That is, the storage unit 17 e stores the parameter “the number ofstandard slot format pilot bits” based on the number of pilot bits inthe uplink DPCCH (Dedicated Physical Control Channel) per wireless framewhen an up slot format to be used is to be changed and all the 15 slotsof one wireless frame are received, and the critical value “the numberof backward protection pilot error allowable bits” for determining pilotbit reception OK in wireless frame synchronization determination, andthe critical value “the number of forward protection pilot errorallowable bits” for determining pilot bit reception NG.

The operation unit 17 a calculates the critical values “the number ofpost-correction backward protection pilot error allowable bits” and “thenumber of post-correction forward protection pilot error allowable bits”for actually determining pilot reception OK/NG from “the number ofstandard slot format pilot bits”, “the number of backward protectionpilot error allowable bits”, and “the number of forward protection piloterror allowable bits” in accordance with the actually received pilotbits per wireless frame.

The parameter “the number of standard slot format pilot bits” describedabove represents the number of pilot bits per wireless frame in thewireless frame structure of the uplink DPCCH as shown in FIGS. 6 to 8.

FIG. 6 shows the wireless frame structure of the uplink DPCCH in theCDMA method. FIG. 7 shows pilot bit patterns when the Npilot data sizesof the uplink DPCCH are 3, 4, 5, and 6 bits. FIG. 8 shows pilot bitpatterns when the Npilot data sizes of the uplink DPCCH are 7 and 8bits.

Referring to FIG. 7, bit#0 and bit#1 of Npilot=3, bit#1 and bit#2 ofNpilot=4, bit#0, bit#1, bit#3, and bit#4 of Npilot=5, and bit#1, bit#2,bit#4, and bit#5 of Npilot=6 are frame synchronization words, and usedto determine wireless frame synchronization.

Likewise, referring to FIG. 8, bit#1, bit#2, bit#4, and bit#5 ofNpilot=7 and bit#1, bit#3, bit#5, and bit#7 of Npilot=8 are framesynchronization words, and used to determine wireless framesynchronization. In FIGS. 7 and 8, pilot bit patterns other than theframe synchronization words are “1”.

Of these pilot bit patterns, selection can be performed from fieldinformation (slot format#0, slot format#2, and slot format#5)corresponding to a normal mode (the number of transmission slots perwireless frame is 15 time slots). That is, “the number of standard slotformat pilot bits” is 90 (unit: bit) if slot format#0 is the standardslot format, and 75 (unit: bit) if slot format#2 or slot format#5 is thestandard slot format.

Also, the correction calculation means 17 and 27 include an SIRdetermination unit 17 c for determining SIR determination OK/NG by usingcritical values “a backward protection SIR threshold value” and “aforward protection SIR threshold value” with respect to the average SIRinformation measured by the decoding means 16 and 26.

The correction calculation means 17 and 27 further include asynchronization establishment determination unit 17 d which determineswhether a state in which pilot bit reception is OK and SIR determinationis OK continues for a predetermined frame period, by using a criticalvalue “the number of frame synchronization backward protection steps”.If this state continues for the predetermined frame period, it isdetermined that wireless frame synchronization establishment isdetected.

Furthermore, the correction calculation means 17 and 27 determinewhether a state in which pilot bit reception is NG or SIR determinationis NG continues for a predetermined frame period, by using a criticalvalue “the number of frame synchronization forward protection steps”. Ifthis state continues for the predetermined frame period, it isdetermined that wireless frame synchronization pull out is detected.

Also, in the baseband processing units 1 and 2 in the node-B, thecorrection calculation means 17 and 27 in the synchronizationdetermination circuits store, in the storage unit 17 e, the criticalvalues “the backward protection SIR threshold value” and “the forwardprotection SIR threshold value” for performing SIR determination OK/NGwith respect to the average SIR per wireless frame calculated by thedecoding means 16 and 26 in the synchronization determination circuits.

The storage unit 17 e has the critical value “the number of framesynchronization backward protection steps” for detecting wireless framesynchronization establishment when the state in which pilot bitreception is OK and SIR determination is OK continues for thepredetermined frame period, and the critical value “the number of framesynchronization forward protection steps” for detecting wireless framesynchronization pull out when the state in which pilot bit reception isNG or SIR determination is NG continues for the predetermined frameperiod.

The critical values “the number of backward protection pilot errorallowable bits” and “the number of forward protection pilot errorallowable bits” described above are 0 (unit: bit) or more, and do notexceed the parameter “the number of standard slot frame pilot bits”.

The critical values “the number of post-correction backward protectionpilot error allowable bits” and “the number of post-correction forwardpilot error allowable bits” as the output results from the correctioncalculation means are calculated byEPilot_revise=(EPilot×Pilot_receive)/Pilot_stand  (1)In equation (1), the solution is rounded off to the nearest wholenumber, EPilot_revise is the critical value “the number ofpost-correction backward protection pilot error allowable bits” or “thenumber of post-correction forward protection pilot error allowablebits”, EPilot is the parameter “the number of backward protection piloterror allowable bits” or “the number of forward protection pilot errorallowable bits”, Pilot_receive is the number of pilot bits received inone wireless frame, and Pilot_stand is the parameter “the number ofstandard slot format pilot bits”.

In the process of calculating EPilot_revise of equation (1), thesolution may also be rounded down or rounded up, instead of beingrounded off, to the nearest whole number.

The critical values “the backward protection SIR threshold value” and“the forward protection SIR threshold value” fall within the range whichthe average SIR per wireless frame measured by the decoding means in thesynchronization determination circuit can take.

The critical values “the number of frame synchronization backwardprotection steps” and “the number of frame synchronization forwardprotection steps” take a value of 0 (unit: step) or more in accordancewith pilot bit reception OK/NG and SIR determination OK/NG.

The recording medium 3 stores programs for implementing the processes ofthe individual means of the baseband processing units 1 and 2 describedabove by using a computer (not shown), and the programs are read outfrom this computer for performing the processes of the basebandprocessing units 1 and 2 and executed.

FIGS. 3 to 5 are flowcharts showing a wireless frame synchronizationdetermination process performed by the correction calculation means 17and 27. The operation of the node-B according to the embodiment of thepresent invention will be explained below with reference to FIGS. 1 to5. Note that the processes in FIGS. 3 to 5 are implemented by executingthe programs stored in the recording medium 3 by the computer forperforming the processes of the baseband processing units 1 and 2.

First, in the node-B, the maximum number of searchable paths is set to10 (unit: path) in the path capture means 12 and 22 in the path searchcircuits 11 and 21, and the number of temporary captured paths allocatednear the propagation delay set from the host apparatus to the node-Bwhen a wireless link is to be set from a state in which no up carrier ispresent is set to 5 (unit: path). Also, parameters and critical valuesto be processed in the synchronization determination circuits 15 and 25and correction calculation means 17 and 27 are predetermined.

As described above, the parameter “the number of standard slot formatpilot bits” can be selected from the field information (slot format#0,slot format#2, and slot format#5) corresponding to the normal mode inthe wireless frame structure of the uplink DPCCH. In this embodiment,slot format#2 is selected as the standard slot format, and “the numberof standard slot format pilot bits” is given as 75 (unit: bit).

The critical values “the number of backward protection pilot errorallowable bits” and “the number of forward protection pilot errorallowable bits” must be 0 (unit: bit) or more, and must not exceed theparameter “the number of standard slot format pilot bits”. In thisembodiment, “the number of backward protection pilot error allowablebits” and “the number of forward protection pilot error allowable bits”are given as 10 (unit: bit) and 15 (unit: bit), respectively.

The critical values “the backward protection SIR threshold value” and“the forward protection SIR threshold value” are set within the rangewhich the average SIR per wireless frame measured by the decoding means16 and 26 can take. In this embodiment, “the backward protection SIRthreshold value” and “the forward protection SIR threshold value” aregiven as 0.0 (unit: dB) and −1.0 (unit: dB), respectively.

The critical values “the number of frame synchronization backwardprotection steps” and “the number of frame synchronization forwardprotection steps” are set to a value of 0 (unit: step) or more inaccordance with pilot bit reception OK/NG and SIR determination OK/NG.In this embodiment, “the number of frame synchronization backwardprotection steps” and “the number of frame synchronization forwardprotection steps” are given as 2 (unit: step) and 10 (unit: step),respectively.

Furthermore, the number of received pilot bits per wireless framedecoded by the decoding means 16 and 26 in the synchronizationdetermination circuits 15 and 25 is set to 90 (unit: bit), i.e., set toslot format#0 of the field information corresponding to the normal modein the wireless frame structure of the uplink DPCCH.

Under the above conditions, the operation of the node-B according tothis embodiment will be described below with reference to FIGS. 1 to 5.In the operation of this embodiment, processing from the setting of awireless link from a state in which no up carrier is present, to thedetection of synchronization establishment in a wireless framesynchronization determination process will be explained.

When detecting a normal path for an input signal from the signal line100, the path capture means 12 in the path search circuit 11 starts acapture process by using temporary path positions allocated near thepropagation delay as reference positions. The path capture means 12operates by this number of temporary captured paths until a normal pathis captured. The path capture means 12 transfers information of thecaptured paths (information of 5 temporary captured paths, to bereferred to as 5-path information hereinafter) to the channel estimationmeans 14 via the signal line 111. The path capture means 12 alsotransfers the 5-path information to the path track transfer means 13 viathe signal line 112.

In accordance with the 5-path information transferred from the pathcapture means 12, the channel estimation means 14 performs channelestimation, RAKE combination, and SIR measurement for each slot, andtransfers the RAKE-combined pilot sequence data and the SIRs ofindividual slots to the decoding means 16 via the signal line 113. Thepath track transfer means 13 stores the 5-path information transferredfrom the path capture means 12.

The decoding means 16 decodes the RAKE-combined pilot data sequenceobtained by the channel estimation means 14, and calculates the averageper wireless frame of the SIRs measured for individual slots. Thedecoding means 16 transfers the decoded pilot bits and the average SIRper wireless frame to the correction calculation means 17 via the signalline 114.

By using the pilot bits and the average SIR per wireless frametransferred from the decoding means 16, the correction calculation means17 first refers to the wireless frame synchronization state of theimmediately preceding frame (step S1 in FIG. 3).

Since in this embodiment the operation starts from the state in which noup carrier is present, the processing starts from the initial state, sothe correction calculation means 17 refers to the setting type aftersetting the wireless frame synchronization state to the initial state(step S9 in FIG. 4).

Since in this embodiment a wireless link is set from the state in whichno up carrier is present, this setting is processed as new setting, sothe correction calculation means 17 sets the setting type to newsetting, and calculates the critical value “the number ofpost-correction backward protection received pilot error allowable bits”by the calculation method of equation (1) by using the preset parameterand critical value.

In this case, the critical value “the number of backward protectionpilot error allowable bits” EPilot is 10 (bits), the parameter “thenumber of standard slot format pilot bits” Pilot_stand is 75 (bits), andthe number of pilot bits received in one wireless frame (slot format#0of the uplink DPCCH) Pilot_receive is 90 (bits), so the critical value“the number of post-correction backward protection pilot error allowablebits” EPilot_revise isEPilot_revise=(10×90)/75=12 (bits)

The correction calculation means 17 sets the critical value “the numberof post-correction backward protection pilot error allowable bits” to 12(unit: bit) and the number of pilot error bits in the decoded pilot datasequence to 10 (unit: bit), and determines “the critical value: thenumber (g) of post-correction backward protection pilot error allowablebits≧the number (b) of pilot error bits in the decoded pilot datasequence” (step S10 in FIG. 4).

In the above example, “the critical value: the number of post-correctionbackward protection pilot error allowable bits=12 bits”, and “the numberof pilot error bits in the decoded pilot data sequence=10 bits”, so thedetermination result is YES, and the correction calculation means 17sets the average SIR per wireless frame at this time to 0.0 (unit: dB),and determines “the critical value: a backward protection SIR thresholdvalue A (h)≦an average SIR (d) per wireless frame” (step S11 in FIG. 4).

In this example, “the critical value: the backward protection SIRthreshold value A=0.0 dB”, and “the average SIR per wireless frame=0.0dB”, so the determination result is YES, and the correction calculationmeans 17 performs processing by which “the number of backward projectionsteps in the present received frame=the number of backward protectionsteps held in the preceding received frame+1 (steps)” (step S12 in FIG.4).

In this processing, the number of backward protection steps held in thepreceding received frame=0, so the number of received frame backwardprotection steps is 1 (unit: step). After that, the correctioncalculation means 17 determines “the number (i) of backward protectionsteps in the present received frame≧the critical value: the number (j)of frame synchronization backward protection steps” (step S14 in FIG.4).

In the above example, the number of backward protection steps in thepresent received frame=1 step, and the critical value: the number offrame synchronization backward protection steps=2 steps, so thedetermination result is NO, and the correction calculation means 17performs processing by which “the wireless frame synchronization statein the present received frame=the initial state, the wireless framesynchronization state in the preceding received frame=the initial state,and the number of backward protection steps in the preceding receivedframe (1 step)=the number of backward protection steps in the receivedframe (1 step)” (step S16 in FIG. 4), and returns to step S1 todetermine wireless frame synchronization in the next received frame.

If the determination results are NO in steps S10 and S11, the number ofbackward protection steps in the present received frame=0 step is set(step S13 in FIG. 4), and the flow advances to the determination in stepS14.

In this embodiment, an operation following the flows shown in FIGS. 3 to5 is performed in the processing of the next received frame. Thecorrection calculation means 17 follows the same process path as aboveto the processing in step S11 of FIG. 4, and then performs processing bywhich “the number of backward protection steps in the present receivedframe=the number of backward protection steps held in the precedingreceived frame+1 (steps)” (step S12 in FIG. 4).

In this processing, the number of backward protection steps held in thepreceding received frame=0 step, so the number of received framebackward protection steps is 2 (unit: step). After that, the correctioncalculation means 17 determines “the number (i) of backward protectionsteps in the present received frame≧the critical value: the number (j)of frame synchronization backward protection steps” (step S14 in FIG.4).

In the above example, the number of backward protection steps in thisframe=2 steps, and the critical value: the number of framesynchronization backward protection steps=2 steps, so the determinationresult is YES, and the correction calculation means 17 performsprocessing by which “the wireless frame synchronization state in thepresent received frame=synchronization establishment, the wireless framesynchronization state of the preceding received frame=synchronizationestablishment, the number (unit: step) of backward protection steps inthe preceding received frame=0 (step), and the number (unit: step) ofbackward protection steps in the preceding received frame=0 (step)”(step S15 in FIG. 4), detects wireless frame synchronizationestablishment, and returns to step S1 to determine wireless framesynchronization in the next received frame.

Processing up to synchronization establishment detection in wirelesslink setting and a wireless frame synchronization determination processwhen different-frequency hard handover control is performed will bedescribed next. When different-frequency hard handover control isperformed, the baseband processing unit 1 becomes unable to continue theprocessing.

In this case, the path capture means 12 in the path search circuit 11always transfers the information of captured normal paths to the pathtrack transfer means 13. The number of the captured paths is 8 (unit:path).

The path track transfer means 13 stores the transferred path informationuntil the baseband processing unit 2 capable of processing is found, andtransfers the stored path information to the path track transfer means23 in the path search circuit 21 of the baseband processing unit 2capable of processing when the baseband processing unit 2 is found.

When detecting a normal path for an input signal duringdifferent-frequency hard handover control, the path capture means 22reads out the path information transferred to the path track transfermeans 23, and operates by the number of the transferred paths until anormal path is captured. The path capture means 22 transfers theinformation of the captured paths (the information of 8 transferredcaptured path, to be referred to as 8-path information hereinafter) tothe channel estimation means 24. Also, the path capture means 22transfers the 8-path information to the path track transfer means 23again.

In accordance with the 8-path information transferred from the capturemeans 22, the channel estimation means 24 performs channel estimation,RAKE combination, and SIR measurement for each slot, and transfers theRAKE-combined pilot sequence data and the SIRs of individual slots tothe decoding means 26 in the synchronization determination circuit 25.The path track transfer means 23 stores the 8-path informationtransferred from the capture means 22.

The decoding circuit 26 in the synchronization determination circuit 25decodes the RAKE-combined pilot data sequence obtained by the channelestimation means 24 in the path search circuit 21, and calculates theaverage per wireless frame of the SIRs measured for individual slots.The decoding means 26 transfers the decoded pilot bits and the averageSIR per wireless frame to the correction calculation means 27 via thesignal line 124.

By using the pilot bits per wireless frame and the average SIRtransferred from the decoding means 26, the correction calculation means27 first refers to the wireless frame synchronization state of thepreceding frame (step S1 in FIG. 3).

Since different-frequency hard handover control is performed in thisembodiment, the processing is started from the initial state. Thecorrection calculation means 27 sets the wireless frame synchronizationstate to the initial state, and refers to the setting type (step S9 inFIG. 4).

Since different-frequency hard handover control is performed in thisembodiment, the processing is handled as intra-cell resynchronizationHHO (Hard HandOver). The correction calculation means 27 sets thesetting type to intra-cell resynchronization HHO, and calculates thecritical value “the number of post-correction backward protectionreceived pilot error allowable bits” by the calculation method ofequation (1) by using the preset parameter and critical value.

In this case, the critical value “the number of backward protectionpilot error allowable bits” EPilot=10 (bits), the parameter “the numberof standard slot format pilot bits” Pilot_stand=75 (bits), and thenumber of pilot bits received in one wireless frame (slot format#0 ofthe uplink DPCCH) Pilot_receive=90 (bits), so the critical value “thenumber of post-correction backward protection pilot error allowablebits” EPilot_revise isEPilot_revise=(10×90)/75=12 (bits)

Accordingly, the correction calculation means 27 sets the critical value“the number of post-correction backward protection pilot error allowablebits” to 12 (unit: bit) and the number of pilot error bits in thedecoded pilot data sequence to 10 (unit: bit), and determines “thecritical value: the number (g) of post-correction backward protectionpilot error allowable bits≧the number (b) of pilot error bits in thedecoded pilot data sequence” (step S17 in FIG. 5).

In the above example, “the critical value: the number of post-correctionbackward protection pilot error allowable bits=12 (bits)”, and “thenumber of pilot error bits in the decoded pilot data sequence=10(bits)”, so the determination result is YES, and the correctioncalculation means 27 sets the average SIR per wireless frame at thistime to 0.0 (unit: dB), and determines “the critical value: a backwardprotection SIR threshold value B (k)≦the average SIR (d) per wirelessframe” (step S18 in FIG. 5).

In the above example, “the critical value: the backward protection SIRthreshold value B=0.0 (dB)”, and “the average SIR per wireless frame=0.0(dB)”, so the determination result is YES, and the correctioncalculation means 27 performs processing by which “the number ofbackward projection steps in the present received frame=the number ofbackward protection steps held in the preceding received frame+1(steps)” (step S19 in FIG. 5).

In this processing, the number of backward protection steps held in thepreceding received frame=0 step, so the number of received framebackward protection steps is 1 (unit: step). After that, the correctioncalculation means 27 determines “the number (i) of backward protectionsteps in the present received frame≧the critical value: the number (j)of frame synchronization backward protection steps” (step S21 in FIG.5).

In the above example, the number of backward protection steps in thepresent received frame=1 step, and the critical value: the number offrame synchronization backward protection steps=2 steps, so thedetermination result is NO, and the correction calculation means 17performs processing by which “the wireless frame synchronization statein the present received frame=the initial state, the wireless framesynchronization state in the preceding received frame=the initial state,and the number of backward protection steps in the preceding receivedframe (1 step)=the number of backward protection steps in the receivedframe (1 step)” (step S23 in FIG. 5), and returns to step S1 todetermine wireless frame synchronization in the next received frame.

If the determination results are NO in steps S17 and S18, the number ofbackward protection steps in the present received frame=0 step is set(step S20 in FIG. 5), and the flow advances to the determination in stepS21.

Even in the processing of the next received frame, the correctioncalculation means 27 operates following the flows shown in FIGS. 3 to 5.The correction calculation means 27 follows the same process path asabove to the processing in step S18 of FIG. 5, and then determines “thenumber (i) of backward protection steps in the present receivedframe≧the critical value: the number (j) of frame synchronizationbackward protection steps” (step S21 in FIG. 5).

In this processing, the number of backward protection steps held in thepreceding received frame=1 step, so the number of received framebackward protection steps is 2 (unit: step). After that, the correctioncalculation means 27 determines “the number (i) of backward protectionsteps in the present received frame≧the critical value: the number (j)of frame synchronization backward protection steps” (step S21 in FIG.5).

In the above example, the number of backward protection steps in thepresent received frame=2 steps, and the critical value: the number offrame synchronization backward protection steps=2 steps, so thedetermination result is YES, and the correction calculation means 27performs processing by which “the wireless frame synchronization stateof the present received frame=synchronization establishment, thewireless frame synchronization state of the preceding receivedframe=synchronization establishment, the number (unit: step) of backwardprotection steps in the preceding received frame=0 (step), and thenumber (unit: step) of backward protection steps in the precedingreceived frame=0 (step)” (step S22 in FIG. 5), detects wireless framesynchronization establishment, and returns to step S1 to determinewireless frame synchronization in the next received frame.

Processing up to synchronization pull out detection in a wireless framesynchronization determination process after wireless framesynchronization establishment detection will be described below. Thepath capture means 12 in the path search circuit 11 of the basebandprocessing unit 1 transfers path capture information of normal paths(information of 2 paths, to be referred to as 2-path informationhereinafter) for an input signal from the signal line 100 to the channelestimation means 14 via the signal line 111. Also, the path capturemeans 12 transfers the 2-path information of the captured paths to thepath track transfer means 13.

In accordance with the 2-path information transferred from the pathcapture means 12, the channel estimation means 14 performs channelestimation, RAKE combination, and SIR measurement for each slot, andtransfers the RAKE-combined pilot sequence data and the SIRs ofindividual slots to the decoding means 16 in the synchronizationdetermination circuit 15. The path track transfer means 13 stores the2-path information transferred from the capture means 12.

The decoding circuit 16 in the synchronization determination circuit 15decodes the RAKE-combined pilot data sequence obtained by the channelestimation means 14 in the path search circuit 11, and calculates theaverage per wireless frame of the SIRs measured for individual slots.The decoding means 16 transfers the decoded pilot bits per wirelessframe and the average SIR to the correction calculation means 17 via thesignal line 114.

By using the pilot bits and the average SIR per wireless frametransferred from the decoding means 16, the correction calculation means17 first refers to the wireless frame synchronization state of thepreceding frame (step S1 in FIG. 3).

In this embodiment, the processing is started from a state in whichwireless frame synchronization is established (step S2 in FIG. 3). Thecorrection calculation means 17 calculates the critical value “thenumber of post-correction backward protection received pilot errorallowable bits” by the calculation method of equation (1) by using thepreset parameter and critical value.

In this case, the critical value “the number of backward protectionpilot error allowable bits” EPilot=15 (bits), the parameter “the numberof standard slot format pilot bits” Pilot_stand=75 (bits), and thenumber of pilot bits received in one wireless frame (slot format#0 ofthe uplink DPCCH) Pilot_receive=90 (bits), so the critical value “thenumber of post-correction backward protection pilot error allowablebits” EPilot_revise isEPilot_revise=(15×90)/75=18 (bits)

Accordingly, the correction calculation means 17 sets the critical value“the number of post-correction backward protection pilot error allowablebits” to 18 (unit: bit) and the number of pilot error bits in thedecoded pilot data sequence to 20 (unit: bit), and determines “thecritical value: the number (a) of post-correction forward protectionpilot error allowable bits<the number (b) of pilot error bits in thedecoded pilot data sequence” (step S2 in FIG. 3).

In the above example, the critical value: the number of post-correctionforward protection pilot error allowable bits=18 (bits), and the numberof pilot error bits in the decoded pilot data sequence=20 (bits), so thedetermination result is YES, and the correction calculation means 17performs processing by which “the number of forward projection steps inthe present received frame=the number of forward protection steps heldin the preceding received frame+1 (steps)” (step S4 in FIG. 3).

In this processing, the number of forward protection steps held in thepreceding received frame=0 step, so the number of received frame forwardprotection steps is 1 (unit: step). After that, the correctioncalculation means 17 determines “the number (e) of forward protectionsteps in the present received frame≧the critical value: the number (f)of frame synchronization forward protection steps” (step S6 in FIG. 3).

In the above example, the number of forward protection steps in thepresent received frame=1 step, and the critical value: the number offrame synchronization forward protection steps=10 steps, so thedetermination result is NO, and the correction calculation means 17performs processing by which “the wireless frame synchronization statein the present received frame=synchronization establishment, thewireless frame synchronization state in the preceding receivedframe=synchronization establishment, and the number of forwardprotection steps in the preceding received frame (1 step)=the number offorward protection steps in the received frame (1 step)” (step S8 inFIG. 3), and returns to step S1 to determine wireless framesynchronization in the next received frame.

Even in the processing of the next received frame, the correctioncalculation means 17 operates following the flows shown in FIGS. 3 to 5.The correction calculation means 17 follows the same process path asabove to determine in step S4 that the number of forward protectionsteps of the present received frame is 10 steps, and then determines“the number (e) of forward protection steps in the present receivedframe≧the critical value: the number (f) of frame synchronizationforward protection steps” (step S6 in FIG. 3).

In the above example, the number of forward protection steps in thepresent received frame=10 steps, and the critical value: the number offrame synchronization forward protection steps=10 steps, so thedetermination result is YES, and the correction calculation means 17performs processing by which “the wireless frame synchronization statein the present received frame=synchronization pull out, the wirelessframe synchronization state of the preceding receivedframe=synchronization pull out, the number (unit: step) of forwardprotection steps in the preceding received frame=0 (step), and thenumber (unit: step) of forward protection steps in the precedingreceived frame=0 (step)” (step S7 in FIG. 3), detects wireless framesynchronization pull out, and returns to step S1 to determine wirelessframe synchronization in the next received frame.

If the determination result is NO in step S2 described above, thecorrection calculation means 17 determines “a forward protection SIRthreshold value (c)>the average SIR (d) per wireless frame” (step S3 inFIG. 3).

If the determination result is NO in step S3, the number of forwardprotection steps in the present received frame=0 step is set (step S5 inFIG. 3), and the flow advances to the determination in step S6. If thedetermination result is YES in S3, the flow advances to step S4.

Note that in the operation of this embodiment, the critical values: thebackward protection SIR threshold value A and backward protection SIRthreshold value B are set and selectively used in accordance with thesetting types. However, it is easy to combine these critical values intoone value or divide them into a plurality of values in accordance withthe wireless characteristic environment. This similarly applies to thecritical values: the forward protection SIR threshold values.

In this embodiment as described above, a temporary captured path is setnear the propagation delay which is set from the host apparatus to thenode-B even in a state in which no up carrier is present, and, whendifferent-frequency hard handover control is to be performed, pathinformation captured by the original resource is transferred to the newresource. Since this makes it possible to shorten the processing timebefore a normal path is captured, it is possible to shorten theprocessing time before synchronization establishment is detected duringwireless frame synchronization determination.

Also, in this embodiment, the wireless frame synchronization methodusing determination by pilot bit patterns and determination by the SIRis provided. This makes it possible to reduce synchronizationestablishment detection errors and synchronization pull out detectionerrors occurring in the conventional methods, and the processing time ofeach detection can be held within a predetermined time by using thecritical values for SIR determination. Consequently, it is possible toreliably detect synchronization establishment, synchronization pull out,and synchronization maintenance during wireless frame synchronizationdetermination, and perform stable wireless frame synchronizationdetermination by which the processing time can be held constant.

In addition, in this embodiment, “the number of standard slot formatpilot bits” is set in determining pilot bit reception OK/NG, and thecritical values for pilot bits as determination conditions are correctedin accordance with changes in wireless frames of the uplink DPCCH.Therefore, perfect wireless frame synchronization determination can beperformed even in a wireless environment in which wireless frames of theuplink DPCCH change during communication.

Furthermore, in this embodiment, when synchronization establishmentdetection, synchronization pull out detection, and synchronizationmaintenance detection are to be performed in a given node-B of anynext-generation mobile communication system using this pilot bit patternand the SIR, the same determination standards common to all systems canbe presented by applying this wireless frame synchronizationdetermination method.

In the above embodiment, in various wireless environments in which hardhandover control is performed or the up slot format to be used changesin the node-B which communicates by using the CDMA method, it ispossible to shorten the time before synchronization establishment isdetected, reduce synchronization establishment detection errors (orsynchronization pull out detection errors) caused by interference,noise, or the like, and perform more reliable wireless framesynchronization detection, by using the path capture means 12 and 22 andpath track transfer means 13 and 23, and performing the wireless framesynchronization method using determination by the pilot bit pattern anddetermination using the SIR.

That is, the wireless base station of the present invention sets atemporary captured path near the propagation delay set from the hostapparatus to the node-B even in a state in which no up carrier ispresent. Also, when different-frequency hard handover control isperformed, path information captured by the original resource istransferred to the new resource. Since this makes it possible to reducethe processing time before a normal path is captured, the processingtime before synchronization establishment is detected during wirelessframe synchronization detection can be reduced.

Another wireless base station of the present invention of the presentinvention provides a wireless frame synchronization method usingdetermination by the pilot bit pattern and determination by the SIR.This makes it possible to reduce synchronization establishment detectionerrors and synchronization pull out detection errors occurring in theconventional methods, and the processing time of each detection can beheld within a predetermined time by using the critical values for SIRdetermination. Consequently, it is possible to reliably detectsynchronization establishment, synchronization pull out, andsynchronization maintenance during wireless frame synchronizationdetermination, and perform stable wireless frame synchronizationdetermination by which the processing time can be held constant.

In addition, in the other wireless base station of the presentinvention, “the number of standard slot format pilot bits” is set indetermining pilot bit reception OK/NG, and the critical values for pilotbits as determination conditions are corrected in accordance withchanges in wireless frames of the uplink DPCCH. Therefore, perfectwireless frame synchronization determination can be performed even in awireless environment in which wireless frames of the uplink DPCCH changeduring communication.

Furthermore, in the present invention, when synchronizationestablishment detection, synchronization pull out detection, andsynchronization maintenance detection are to be performed in a givennode-B of any next-generation mobile communication system using thispilot bit pattern and the SIR, the same determination standards commonto all systems can be presented by applying the wireless framesynchronization determination method described above.

As described above, the wireless base station according to the presentinvention, the wireless frame synchronization detection method usedtherein, and the recording medium on which a program therefor isrecorded are particularly suitably used in a wireless base state(node-B) which communicates by the CDMA (Code Division Multiple Access)method.

1. A wireless base station which communicates by a Code DivisionMultiple Access (CDMA) method, the wireless base station comprising:path capture means for setting a temporary captured path near a presetpropagation delay when a signal is received from a state in which noupward signal is input, and performing a normal path capture process forthe input signal; channel estimation means for performing channelestimation, RAKE combination, and signal to interference ratiomeasurement per slot for a path captured by said path capture means;decoding means for decoding a RAKE combined pilot data sequence obtainedby said channel estimation means, and calculating an average perwireless frame of the signal to interference ratios measured forindividual slots; and correction calculation means for determiningwhether pilot bit reception is OK or NG on the basis of pilot bitinformation per wireless frame decoded by said decoding means, anddetermining whether signal to interference ratio determination is OK orNG with respect to signal to interference ratio average informationmeasured by said decoding means; wherein said correction calculationmeans comprises a pilot bit determination unit which determines whetherpilot bit reception is OK or NG, an SIR determination unit whichdetermines whether signal to interference ratio determination is OK orNG, and a synchronization establishment determination unit whichdetermines wireless frame synchronization by using results of thedetermination of pilot bit reception OK/NG and the determination ofsignal to interference ratio determination OK/NG.
 2. A wireless basestation according to claim 1, further comprising path track transfermeans for transferring path information captured by said path capturemeans to a new resource which performs processing if the processingcannot be performed due to hard handover control, wherein said pathcapture means performs the normal path capture process by using the pathinformation from the original resource.
 3. A wireless base stationaccording to claim 1, wherein said pilot bit determination unitdetermines whether pilot bit reception is OK or NG on the basis of aparameter based on the number of pilot bits in an uplink DedicatedPhysical Control Channel (DPCCH) per wireless frame when all slots ofone wireless frame are received when an up slot format to be usedchanges, and a critical value for performing the determination of pilotbit reception OK/NG in wireless frame synchronization determination. 4.A wireless base station according to claim 1, wherein said SIRdetermination unit determines whether signal to interference ratiodetermination is OK or NG on the basis of a critical value forperforming the determination of signal to interference ratiodetermination OK/NG with respect to the signal to interference ratioaverage information measured by said decoding means.
 5. A wireless basestation according to claim 1, wherein said synchronization establishmentdetermination unit detects wireless frame synchronization establishmentif a state in which it is determined that pilot bit reception is OK andsignal to interference ratio determination is OK continues for apredetermined frame period.
 6. A wireless base station according toclaim 1, wherein said synchronization establishment determination unitdetects wireless frame synchronization pull out if a state in which itis determined that pilot bit reception is NG or a state in which it isdetermined that signal to interference ratio determination is NGcontinues for a predetermined frame period.
 7. A wireless base stationaccording to claim 1, wherein said correction calculation means furthercomprises an operation unit which calculates a critical value fordetermining whether pilot bit reception is OK or NG in wireless framesynchronization determination.
 8. A wireless base station according toclaim 2, wherein said channel estimation means comprises: an estimationunit which performs channel estimation for a path captured by said pathcapture means; a RAKE combination unit which performs RAKE combination;and an SIR measurement unit which measures a signal to interferenceratio for each slot, and said decoding means comprises: a decoding unitwhich decodes a RAKE combined pilot data sequence obtained by saidchannel estimation means; and an averaging unit which calculates anaverage per wireless frame of signal to interference ratios measured forindividual slots.
 9. A wireless base station according to claim 1,wherein said path capture means comprises: a capture path allocationunit which sets a temporary captured path near a preset propagationdelay when a signal is received from a state in which no upward signalis input; and a normal path capture unit which performs a normal pathcapture process for the input signal.
 10. A wireless framesynchronization detection method of determining wireless framesynchronization in a wireless base station which communicates by a (CodeDivision Multiple Access (CDMA) method, the wireless framesynchronization detection method comprising: setting a propagationdelay; setting a temporary captured path near the propagation delay whena signal is received from a state in which no upward signal is input;performing a normal path capture process for the input signal;performing channel estimation, RAKE combination, and signal tointerference ratio measurement per slot for a path captured by thenormal path capture process; decoding a RAKE combined pilot datasequence; calculating an average per wireless frame of the signal tointerference ratios measured for individual slots; determining whetherpilot bit reception is OK or NG on the basis of decoded pilot bitinformation per wireless frame; determining whether signal tointerference ratio determination is OK or NG with respect to signal tointerference ratio average information; and determining wireless framesynchronization by using results of the determination of pilot bitreception OK/NG and the determination of signal to interference ratiodetermination OK/NG.
 11. A wireless frame synchronization detectionmethod according to claim 10, further comprising: transferring pathinformation captured by the normal path capture process to a newresource which performs processing if the processing cannot be performeddue to hard handover control; and performing the normal path captureprocess by using the path information from an original resource.
 12. Awireless frame synchronization detection method according to claim 10,wherein said determining whether pilot bit reception is OK or NGcomprises determining whether pilot bit reception is OK or NG on thebasis of a parameter based on the number of pilot bits in an uplinkDedicated Physical Control Channel (DPCCH) per wireless frame when allslots of one wireless frame are received when an up slot format to beused changes, and a critical value for performing the determination ofpilot bit reception OK/NG in wireless frame synchronizationdetermination.
 13. A wireless frame synchronization detection methodaccording to claim 10, wherein said determining whether signal tointerference ratio determination is OK or NG comprises determiningwhether signal to interference ratio determination is OK or NG on thebasis of a critical value for performing the determination of signal tointerference ratio determination OK/NG with respect to signal tointerference ratio average information.
 14. A wireless framesynchronization detection method according to claim 10, wherein saiddetermining wireless frame synchronization comprises detecting wirelessframe synchronization establishment if a state in which it is determinedthat pilot bit reception is OK and signal to interference ratiodetermination is OK continues for a predetermined frame period.
 15. Awireless frame synchronization detection method according to claim 10,wherein said determining wireless frame synchronization detects wirelessframe synchronization pull out if a state in which it is determined thatpilot bit reception is NG or a state in which it is determined thatsignal to interference ratio determination is NG continues for apredetermined frame period.
 16. A computer readable recording mediumrecording a program of a wireless frame synchronization detection methodof determining wireless frame synchronization in a wireless base stationwhich communicates by a Code Division Multiple Access (CDMA) method,wherein said program comprises a program which allows a computer tofunction as: path capture means for setting a temporary captured pathnear a preset propagation delay when a signal is received from a statein which no upward signal is input, and performing a normal path captureprocess for the input signal; channel estimation means for performingchannel estimation, RAKE combination, and signal to interference ratiomeasurement per slot for a path captured by the normal path captureprocess; decoding means for decoding a RAKE combined pilot datasequence, and calculating an average per wireless frame of the signal tointerference ratios measured for individual slots; and correctioncalculation means for performing the wireless frame synchronizationdetermination by determining whether pilot bit reception is OK or NG onthe basis of decoded pilot bit information per wireless frame, anddetermining whether signal to interference ratio determination is OK orNG with respect to signal to interference ratio average information. 17.A computer readable recording medium according to claim 16, furthercomprising a program which allows a computer to function as path tracktransfer means for transferring path information captured by the normalpath capture process to a new resource which performs processing if theprocessing cannot be performed due to hard handover control, and as pathcapture means for performing the normal path capture process by usingthe path information from an original resource.